Metal roofs hang tough in all kinds of weather

Mike McClintockSPECIAL TO THE TRIBUNE

The best protection against stormy weather might be a poured concrete house with a solid masonry roof. But you don't have to build a bunker to keep out the weather. Instead, consider a practical upgrade to standard asphalt shingles: metal. It costs more up front but pays dividends long term in minimal maintenance and durability.

Most residential roofs have asphalt shingles that last about 20 years.

Asphalt isn't the most popular because it's the best looking or most durable. It wins because the longer-lasting alternatives cost more, a lot more. Slate, for example, can run four times the price of asphalt on a basic Cape, and becomes exponentially more expensive on a complex roof with dormers and valleys.

But the hidden drawback of super roofs like slate, terra cotta and concrete tile is their weight. It's good for resisting wind uplift and other storm damage. But you have to build an unusually solid, often specially engineered frame to support it. That's costly on new homes and almost impossible after the fact on renovations. Even if you dismantle the existing roof and install much beefier rafters, the house walls will probably need strengthening to carry the load.

A practical compromise that's long lasting and still workable on standard construction is metal. Many metal manufacturers offer a 50-year warranty. But the Metal Roofing Alliance, a Washington-state-based trade group, says metal can last more than 60 years, a period in which even premium asphalt shingles will likely need two reroofing jobs.

And metal is lighter than concrete tile, so it doesn't require extraordinary framing. It's even lighter than asphalt shingles, and can be used for reroofing where the existing surface is sound and local codes permit. Here are the stats. Metal typically weighs 1.5 to 2 pounds per square foot. Asphalt shingles weigh 2 to 5 a square foot (depending on shingle grade). Wood shakes weigh 3 to 4 a square foot. Tile and slate is generally 6 a square foot, while concrete tile weighs 9 to 11 a square foot.

We're not talking about shiny tin on top of a barn. Modern residential metal comes in many configurations, including panels shaped as individual tiles, shingles, and shakes. The most common type is called standing steam -- long panels running from the ridge to the eaves that are connected with a sealed, rollover joint. There is lighter, less sturdy aluminum, and elegant, pricey copper.

But the most common metal roof is steel, typically zinc-coated against corrosion and then sealed. The most durable finishes (available in many colors) are known by their trade names, Kynar-500 and Hylar-5000. For a look, try the Alliance Web site (metalroofing.com), which offers a photo gallery plus links to manufacturers and contractors.

Most metal systems are installed with hidden fasteners. Clips are screwed to the plywood roof sheathing, and then roofing panels are fastened to the clips.

You don't see any fasteners on the surface. Configurations vary, but on long, straight runs, installers often use a metal molding machine to finish seams.

The result is an interlocked metal shield that won't easily separate and blow apart in high winds. In building code language it's called uplift resistance.

The director of engineering for the Ohio-based Metal Building Manufacturers Association puts it this way. "A properly designed and constructed metal roof won't rip, tear, puncture, shrink, creep, slip, blow off or burn."

Although cost varies by roof type and other factors, standing-seam metal initially costs about twice as much as asphalt shingles. But the sticker shock fades after 15 or 20 years when asphalt needs to be reroofed and metal needs only another spritz with a garden hose. On a typical house, the Alliance says that's when overall costs for asphalt surpass the price of no-maintenance metal by about $2,000. Over a predicted 60-year lifespan for metal, additional asphalt reroofing work makes the investment look even better.